Improvement of Frequency Characteristics for Defected Ground Structure Resonators

New techniques of designing a compact coplanar-waveguide (CPW) harmonic-suppressed resonator -using the defected ground structure (DGS) resonator with floating or shorting patches are proposed in this paper. Two T-shaped slots as a bandstop resonator are etched in two ground planes of a CPW 50V transmission line. Two rectangular patches are symmetrically placed on the bottom layer of the substrate. The patches modeled as an additional capacitance increase the effective capacitance of the resonator. By tuning the -geometrical dimension of the patches, the resonant frequency is lowered. Furthermore, frequency -reduction and harmonic suppression are improved by embedding two shorting pins or adding two shorting walls inside the patches. The rejection bandwidth decreases and the quality factor (Q) increases due to -enhancement of stored energy in the resonator.